Current ink cartridges for inkjet printers can be generally divided into two categories based on the connection mode of the ink cartridge to the printhead. One category is the all-in-one printhead-ink cartridge having a printhead connected to the ink cartridge by non-removable means, wherein the printhead usually uses thermal inkjet printing technology and the ink is usually directly stored inside a printhead chamber with the cartridge cover non-removably connected to the printhead chamber by welding. After the ink inside the printhead chamber is depleted, the entire ink cartridge together with the printhead is required to be replaced, resulting in high costs both in manufacturing and in using the printing consumables. As a result, it causes not only unnecessary wastes but also environment pollution by large amount of this mixed electronic waste which is difficult to dispose of and recycle. The other category is a segregated printhead-ink cartridge having the printhead connected to the ink cartridge by removable means, wherein the printhead usually uses piezoelectric printing technology and the ink is stored inside an ink cartridge housing. After the ink inside the ink cartridge housing is depleted, what is needed is just to replace the ink cartridge. Although the printhead can be repeatedly used many times, with only the ink cartridge as a disposable consumable which has relatively low manufacture cost and use cost, the cost of replacing the printhead is high due to the fact that the cost of a printhead using the piezoelectric printing technology is much higher in comparison with that of the printhead using the thermal inkjet printing technology. The cost of replacing such type of printhead is typically about 50% of the total cost of the printer. Besides, replacing the printhead is more difficult since this can only be done by designated qualified technicians through the dismantlement of the printer.
In light of the problems existing in the all-in-one printhead-ink cartridges, ink cartridges which can be refilled with ink are already available in the market. However, very complicated techniques are required for the ink refill operation and it is often too difficult for ordinary users to master them. Furthermore, the following problems occur very often when performing such an operation: (1) chemical reactions occur between the added ink and the ink remaining inside the cartridge when these inks are not compatible, resulting in ink deterioration and even blockage of the printhead nozzles; (2) the printhead's contact-type electric circuits are easily polluted by the ink causing improper electrical contact and printhead failure; (3) the printhead is easily damaged by external impact forces during handling; and (4) after repeated refills of ink, more and more ink residues are deposited on the surfaces of both the ink-absorbent materials and the ink filters and these residues are difficult to be removed, therein resulting in blockage of the ink filters. Due to the existence of the aforementioned problems, the actual number of ink refills is quite limited. Therefore the use life of the printhead cannot be practically and effectively prolonged and the printing quality cannot be reliably assured. Sometimes printing cannot even be carried out.
Directed against the problems existing in the all-in-one printhead-ink cartridges, segregated printhead-ink cartridges are also available where the ink cartridge is connected to the printhead by removable means. The ink cartridge is disposable while the printhead can be recycled for re-use. However, when the printhead is connected to the ink cartridge at the first time, the printhead must be processed by means of a complicated mechanical method. Therefore, a complete set of printhead and ink cartridge provided by special manufacture must be used. This results in limited adaptability of the products. Besides, since the resilient sealing member used for connecting the ink-supply port of the ink cartridge to the ink channel of the printhead nozzles is dependent on a circular groove surrounding the cylindrical surface on the outside of the sealing member matching with the ink-outlet of the ink cartridge by a clearance-fit, the clearance-fit area is in an unsealed condition when no other external pressure is applied. Each corresponding surface in the fitting is in surface-to-surface contact and the sealing for such a contact requires not only smooth and flat contact surfaces, but also a large contact pressure. Therefore, problems may occur due to an unreliable sealing condition existing at the contacting surfaces between the sealing member and the ink cartridge or due to the difficulties in unloading and loading the ink cartridge resulting from the large contact pressure. Furthermore, due to the miniature semi-circular cross-section seal line existing on the external end surface of the sealing member, the welding edge of the ink filter within the printhead chamber, which contacts the said seal line, is very narrow and the contact formed is almost line-to-line. Consequently, a problem of mismatch in position would easily occur, resulting in an unreliable seal at the area where the sealing member is in contact with the welding edge. In addition to the aforementioned problems, since the ink cartridge is fixed within the printhead by means of locking the external raised ribs of the ink cartridge into the grooves on the inner walls of the printhead chamber and the all-around-completely-sealed ink cartridge and the walls of the printhead chamber are basically non-elastic, it is not only that it is extremely difficult to load the ink cartridge into the printhead chamber due to the difficulties in locking the said raised ribs into the said grooves, but also that it is even more difficult for the dismantlement due to more difficulties in removing the said raised ribs out of the said grooves. Ordinary users usually cannot perform these operations of dismantlement and assembly.